<template>
  <div class="todo-footer">
    <label>
      <input type="checkbox" :checked="isAllCheck"/>
    </label>
    <span>
      <span>已完成{{doneSize}}</span> / 全部{{ todos.length }}
    </span>
    <button class="btn btn-danger" v-if="doneSize>0" @click="deleteAllDone">清除已完成任务</button>
  </div>
</template>

<script>
export default {
  name: 'Footer',

  // 声明接收属性 => 接收的属性就会自动成为组件对象的属性
  // props: ['todos'],
  props: {
    // todos: Array
    todos: {
      type: Array,
      required: true
    },
    deleteAllDone: {
      type: Function,
      required: true
    }
  },
  computed: {
    // 完成的数量
    doneSize () {
      return this.todos.reduce((pre, item) => pre + (item.done ? 1 : 0), 0)
    },

    // 是否选中全选checkbox
    isAllCheck () {
      return this.doneSize === this.todos.length  && this.doneSize>0
    }
  }
}
</script>

<style scoped>
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}

</style>

